The present invention is directed to a belt tensioner for a transmission belt system, and more specifically, to an improved damper assembly for the belt tensioner and a method for constructing the belt tensioner incorporating the improved damper assembly.
The main purpose of an automatic belt tensioner is to prolong the life of an engine or accessory drive belt. The most typical use for such automatic belt tensioners is on front-end accessory drives in an automobile engine. This drive includes pulley sheaves for each accessory the belt is required to power, such as the air conditioner, water pump, fan and alternator. Each of these accessories requires varying amounts of power at various times during operation. These power variations, or torsionals, create a slackening and tightening situation of each span of the belt. The belt tensioner is utilized to absorb these torsionals through use of an internally mounted torsion spring. Reference can be made to U.S. Pat. Nos. 5,545,095 or 5,803,850 (each of which are incorporated herein by reference) for examples of prior art belt tensioners.
The automatic belt tensioner will include a tension arm pivotally mounted to a base housing or spring case, where the torsion spring is operatively coupled between the tension arm and the base housing so as to force the distal end of the tension arm against the drive belt, and in turn, to provide sufficient tension force on the drive belt as desired. The size of torsional loads experienced by the drive belt is sometimes large enough to significantly move the tension arm away from the belt, causing the tension in the belt to be temporarily reduced. This is not favorable above a certain degree and squealing and squeaking of the belt may result. Therefore, typical belt tensioners incorporate dampening devices to slow the pivotal movement of the tension arm.
The present invention provides a belt tensioner for a transmission belt system that includes an improved damper assembly; and furthermore, a method for manufacturing such a belt tensioner that includes the improved damper assembly.
A first aspect of the present invention is directed to a belt tensioner for a power transmission belt system that includes (a) a base housing including a pivot shaft extending therefrom; (b) a tension arm pivotally mounted on the pivot shaft at a proximal end thereof, the proximal end of the tension arm including a rub surface and the distal end of the tension arm adapted to contact a power transmission belt; (c) a torsion spring operatively coupled between the base and the tension arm and adapted to bias the distal end of the tension arm against the power transmission belt; and (d) a damper assembly coupled to the housing, the damper assembly including: (1) a body of friction material that includes a friction surface adjacent to and facing the rub surface of the tension arm and (2) a damper spring integral with the body of friction material and biasing the body of friction material and associated friction surface against the rub surface of the tension arm.
In a more detailed embodiment, the damper assembly is substantially disk shaped and coaxially mounted on the pivot shaft. In a further detailed embodiment, the damper spring is an annular metallic spring plate coaxially integrated with a substantially disk-shaped body of friction material. In yet a further detailed embodiment, the spring plate has a generally conical shape and includes a convex side facing toward the rub surface of the tension arm, where the generally conical shape of the spring plate biases the body of friction material axially against the rub surface of the tension arm. In yet a further detailed embodiment, the damper assembly includes an annular flange extending at least partially axially towards the tension arm and encircling an annular shoulder of the tension arm, thereby providing a labyrinth seal between the damper assembly and the tension arm. In yet a further detailed embodiment, the annular flange extends from the body of the friction material.
In an alternative detailed embodiment of the first aspect of the present invention, the body of friction material is molded over the damper spring. In a further detailed embodiment, the body of friction material is a wear-resistant plastic material. In a further detailed embodiment, the body of friction material is substantially disk shaped, and the damper spring is an annular metallic spring plate coaxially molded with the substantially disk-shaped body of friction material and the annular metallic spring plate biases the body of friction materially axially against the rub surface of the tension arm. In a further detailed embodiment, the annular metallic spring plate is coaxially attached to the pivot shaft of the base housing, and the proximal end of the tension arm is retained axially between the damper assembly and the base housing by the coaxially attachment of the annular metallic spring plate and pivot shaft.
In an alternate detailed embodiment of the first aspect of the present invention, the damper assembly is mounted to the base housing, coaxially with the pivot shaft, and includes an annular flange extending at least partially axially towards the tension arm and encircling an annular shoulder of the tension arm, thereby providing a labyrinth seal between the damper assembly and the tension arm. In a further detailed embodiment, the annular flange extends from the body of friction material. In an even further detailed embodiment the annular flange extending from the damper assembly has an inner diameter slightly larger than the outer diameter of the annular shoulder of the tension arm.
A second aspect of the present invention is directed to a belt tensioner for a power transmission belt system that includes: (a) a base housing including a pivot shaft extending therefrom; (b) a tension arm pivotally mounted on the pivot shaft at a proximal end thereof, where the proximal end of the tension arm includes a rub surface and the distal end of the tension arm is adapted to contact a power transmission belt; (c) a torsion spring operatively coupled between the base and the tension arm, and adapted to bias the distal end of the tension arm against the power transmission belt; and (d) a damper assembly coupled to the housing, where the damper assembly includes: (1) an annular spring plate coaxially attached to the pivot shaft of the base housing and (2) a body of friction material having at least a portion positioned axially between the annular spring plate and the rub surface of the tension arm; (e) where the body of friction material includes a friction surface adjacent to and facing the rub surface of the tension arm; and (f) where the annular spring plate biases the body of friction material and associated friction surface against the rub surface of the tension arm and retains the proximal end of the tension arm and the body of friction material axially between the annular spring plate and the base housing.
In a further detailed embodiment of the second aspect of the present invention described above, the body of friction material is annular and is positioned coaxially with the pivot shaft, and includes an annular flange extending at least partially axially toward the tension arm and encircling an annular shoulder of the tension arm, thereby providing a labyrinth seal between the body of friction material and the tension arm. In a further detailed embodiment, the annular flange extending from the damper assembly has an inner diameter that is slightly larger than the outer diameter of the annular shoulder of the tension arm. And in a further detailed embodiment, the body of friction material is molded over the annular spring late.
In an alternate detailed embodiment of the second aspect of the present invention described above, the body of the friction material is molded over the annular spring plate.
In another alternate embodiment of the second aspect of the present invention described above, the body of friction material is substantially annular and coaxially positioned with respect to the pivot shaft. In a more detailed embodiment, the rub surface of the tension arm and the friction surface of the body of friction material are substantially annular, coaxial with the pivot shaft, and residing on parallel planes at least partially perpendicular to the access of the pivot shaft.
A third aspect of the present invention is directed to a belt tensioner for a power transmission belt system that includes: (a) a base housing; (b) a tension arm pivotally mounted on the base housing at a proximal end of the tension arm, where the proximal end of the tension arm includes a rub surface and the distal end of the tension arm is adapted to contact a power transmission belt; (c) a torsion spring operatively coupled between the base housing and the tension arm, and adapted to bias the distal end of the tension arm against the power transmission belt; and (d) a damper assembly coupled to the housing, where the damper assembly includes: (1) a body of friction material having a friction surface adjacent to and facing the rub surface of the tension arm, and (2) a damper spring biasing the body of friction material and associated friction surface against the rub surface of the tension arm; (e) where the damper assembly includes an annular flange extending at least partially axially towards the tension arm, and the flange encircles an annular shoulder of the tension arm, thereby providing a labyrinth seal between the body of friction material and the tension arm.
In a more detailed embodiment of the third aspect of the present invention described above, the annular flange extending from the damper assembly has an inner diameter that is slightly larger than the outer diameter of the annular shoulder of the tension arm. In a further detailed embodiment, the body of friction material encircles the pivot shaft and the annular flange extends from the body of the friction material. In an even further detailed embodiment, the body of friction material is molded over the annular spring plate.
In a fourth aspect of the present invention, a belt tensioner for a power transmission belt system comprises: (a) a base housing; (b) a tension arm pivotally mounted on the base housing at a proximal end of the tension arm, where the proximal end of the tension arm includes a rub surface and the distal end of the tension arm is adapted to contact a power transmission belt; (c) a torsion spring operatively coupled between the base housing and the tension arm, and adapted to bias the distal end of the tension arm against the power transmission belt; (d) a damper assembly coupled to the base housing, where the damper assembly includes: (1) a body of friction material having a friction surface adjacent to and facing the rub surface of the tension arm and (2) a damper spring biasing the body of friction material and associated friction surface against the rub surface of the tension arm; and (e) a labyrinth seal provided between the damper assembly and the tension arm.
In a more detailed embodiment of the fourth aspect of the present invention described above, the labyrinth seal includes an annular flange extending from one of the damper assembly or the tension arm at least partially axially towards the other of the damper assembly and the tension arm, and the flange encircles an annular shoulder of the other one of the damper assembly and the tension arm.
In an alternate detailed embodiment of the fourth aspect of the present invention described above, the labyrinth seal includes an annular flange extending from one of the body of friction material and the tension arm at least partially axially towards the other of the body of friction material and the tension arm, and the flange encircles the annular shoulder of the other of the body of friction material and the tension arm.
In a fifth aspect of the present invention, a method for assembling a belt tensioner is provided that includes the steps of: (a) providing a base housing including a pivot shaft; (b) positioning a torsion spring on the pivot shaft; (c) positioning a proximal end of the tension arm on the pivot shaft, where the proximal end of the tension arm includes a rub surface at least partially encircling the pivot shaft; (d) coupling the torsion spring between the base housing and the pivot shaft; (e) positioning a friction body axially over the proximal end of the tension arm such that a friction surface of the friction body faces the rub surface of the tension arm; and (f) fixedly attaching a substantially annular spring plate axially over at least a portion of the friction body to retain the proximal end of the tension arm and a portion of the friction body axially between the base housing and the spring plate and to bias the friction surface of the friction body against the rub surface of the tension arm.
In a more detailed embodiment of the method of the fifth aspect of the present invention, the method further comprises the steps of deforming a substantially planer annular plate in a generally conical shape to provide the annular spring plate, simultaneous to or prior to the fixedly attaching step. In an even more detailed embodiment of this method, the annular spring plate has a center hole that includes an inner circumferential surface with a plurality of teeth extending radially inwardly therefrom, and the fixedly attaching step includes a step of expanding the diameter of the hollow upper end of the pivot shaft to radially force the outer circumferential, surface of the center hole in the annular spring plate, thereby causing the annular teeth to become embedded into the pivot shaft.
In an alternate detailed embodiment of the method described in the fifth aspect of the present invention, the method further comprises the step of, prior to the fixedly attaching step, molding the friction body over the annular spring plate. In an even further detailed embodiment, the method further comprises the step of deforming a substantially planar annular plate in a generally conical shape to provide the annular spring plate, simultaneous to or prior to the fixedly attaching step. This deforming step may occur prior to the molding step or after the molding step.
In another alternate detailed embodiment of the fifth aspect of the present invention described above, the method further comprises the step of providing a labyrinth seal between the friction body and the tension arm. In a further detailed embodiment, the method further comprises the step of, prior to the fixedly attaching step, molding the friction body over the annular spring plate. In an even further detailed embodiment, the tension arm includes an annular shoulder coaxial with the pivot shaft, the molding step includes a step of molding an annular flange extending at least partially axially from the friction body, where the annular flange has a diameter slightly larger than the diameter of the annular shoulder of the tension arm, and the step of positioning a friction body axially over the proximal end of the tension arm includes the step of encircling the annular shoulder of the tension arm with the annular flange extending from the friction body to provide a labyrinth seal between the friction body and the tension arm.